Polymer, resist composition and patterning process

ABSTRACT

A polymer comprising recurring units of formula (1) and having a Mw of 1,000-500,000 is provided.                    
     R 1  is H, methyl or CH 2 CO 2 R 3 , R 2  is H, methyl or CO 2 R 3 , R 3  is alkyl, R 4  is H, alkyl, alkoxyalkyl or acyl, R 5  and R 15  are acid labile groups, and at least one of R 6  to R 9  is a carboxyl or hydroxyl-containing monovalent hydrocarbon group, and the remainders are H or alkyl, at least one of R 10  to R 13  is a monovalent hydrocarbon group containing a —CO 2 — partial structure, and the remainders are H or alkyl, R 14  is a polycyclic hydrocarbon group or polycyclic hydrocarbon-containing alkyl group, Z is a trivalent hydrocarbon group, X is —CH 2 — or —O—, k=0 or 1, x is&gt;0, a, b, c and d are≧0, satisfying x+a+b+c+d=1. A resist composition comprising the polymer has significantly improved sensitivity, resolution and etching resistance and is very useful in microfabrication.

This invention relates to (1) a polymer comprising specific units with arobust alicyclic structure having both polar groups and acid labilegroups, (2) a resist composition comprising the polymer as a base resin,having improved reactivity, substrate adhesion and etching resistance,and especially suited as micropatterning material for VLSI fabrication,and (3) a patterning process using the resist composition.

BACKGROUND OF THE INVENTION

While a number of recent efforts are being made to achieve a finerpattern rule in the drive for higher integration and operating speeds inLSI devices, deep-ultraviolet lithography is thought to hold particularpromise as the next generation in microfabrication technology. Inparticular, photolithography using a KrF or ArF excimer laser as thelight source is strongly desired to reach the practical level as themicropatterning technique capable of achieving a feature size of 0.3 μmor less.

The resist materials for use in photolithography using light of anexcimer laser, especially ArF excimer laser having a wavelength of 193nm, are, of course, required to have a high transmittance to light ofthat wavelength. In addition, they are required to have an etchingresistance sufficient to allow for film thickness reduction, a highsensitivity sufficient to eliminate any extra burden on the expensiveoptical material, and especially, a high resolution sufficient to form aprecise micropattern. To meet these requirements, it is crucial todevelop a base resin having a high transparency, rigidity andreactivity. None of the currently available polymers satisfy all ofthese requirements. Practically acceptable resist materials are not yetavailable.

Known high transparency resins include copolymers of acrylic ormethacrylic acid derivatives and polymers containing in the backbone analicyclic compound derived from a norbornene derivative. All theseresins are unsatisfactory. For example, copolymers of acrylic ormethacrylic acid derivatives are relatively easy to increase reactivityin that highly reactive monomers can be introduced and acid labile unitscan be increased as desired, but difficult to increase rigidity becauseof their backbone structure. On the other hand, the polymers containingan alicyclic compound in the backbone have rigidity within theacceptable range, but are less reactive with acid thanpoly(meth)acrylate because of their backbone structure, and difficult toincrease reactivity because of the low freedom of polymerization.Therefore, some resist compositions which are formulated using thesepolymers as the base resin, fail to withstand etching although they havesatisfactory sensitivity and resolution. Some other resist compositionsare highly resistant to etching, but have low sensitivity and lowresolution below the practically acceptable level.

SUMMARY OF THE INVENTION

An object of the invention is to provide (1) a polymer having improvedreactivity, rigidity and substrate adhesion, (2) a resist compositioncomprising the polymer as a base resin and achieving significantlysurpassing sensitivity, resolution and etching resistance over prior artcompositions, and (3) a patterning process using the resist composition.

It has been found that a polymer comprising recurring units of thefollowing general formula (1) and having a weight average molecularweight of 1,000 to 500,000 possesses improved reactivity, rigidity andsubstrate adhesion, and that a resist composition using the polymer as abase resin has a high sensitivity, high resolution and high etchingresistance and is very useful in precise microfabrication.

In one aspect, the invention provides a polymer comprising recurringunits of the following general formula (1) and having a weight averagemolecular weight of 1,000 to 500,000.

Herein R¹ is hydrogen, methyl or CH₂CO₂R³; R² is hydrogen, methyl orCO₂R³; R³ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms; R⁴ is hydrogen, a straight, branched or cyclic alkyl groupof 1 to 15 carbon atoms, a straight, branched or cyclic alkoxyalkylgroup of 2 to 15 carbon atoms, or a straight, branched or cyclic acylgroup of 1 to 15 carbon atoms; R⁵ and R¹⁵ each are an acid labile group;at least one of R⁶ to R⁹ is a carboxyl or hydroxyl-containing monovalenthydrocarbon group of 1 to 15 carbon atoms, and the remainders areindependently hydrogen or a straight, branched or cyclic alkyl group of1 to 15 carbon atoms, or R⁶ to R⁹, taken together, may form a ring, andwhen they form a ring, at least one of R⁶ to R⁹ is a carboxyl orhydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms,and the remainders are independently a single bond or a straight,branched or cyclic alkylene group of 1 to 15 carbon atoms; at least oneof R¹⁰ to R¹³ is a monovalent hydrocarbon group of 2 to 15 carbon atomscontaining a —CO₂— partial structure, and the remainders areindependently hydrogen or a straight, branched or cyclic alkyl group of1 to 15 carbon atoms, or R¹⁰ to R¹³, taken together, may form a ring,and when they form a ring, at least one of R¹⁰ to R¹³ is a divalenthydrocarbon group of 1 to 15 carbon atoms containing a —CO₂— partialstructure, and the remainders are independently a single bond or astraight, branched or cyclic alkylene group of 1 to 15 carbon atoms; R¹⁴is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkylgroup containing such a polycyclic hydrocarbon group; Z is a trivalenthydrocarbon group of 1 to 10 carbon atoms, or Z forms a ring with R¹,and in this event, R¹ is methylene and Z is a tetravalent hydrocarbongroup of 1 to 10 carbon atoms; X is —CH₂— or —O—; k is equal to 0 or 1,x is a number of more than 0, a, b, c and d are 0 or positive numbers,satisfying x+a+b+c+d=1.

Preferably, the acid labile groups represented by R⁵ and R¹⁵ in formula(1) are selected from the class consisting of groups of the followinggeneral formulae (L1) to (L4), tertiary alkyl groups of 4 to 20 carbonatoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbonatoms, oxoalkyl groups of 4 to 20 carbon atoms, and mixtures of any ofthe foregoing.

Herein R^(L01) and R^(L02) each are hydrogen or a straight, branched orcyclic alkyl group of 1 to 18 carbon atoms; R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms which may contain a heteroatom such as oxygen atom; a pair of R^(L01) and R^(L02), R^(L01) andR^(L03), or R^(L02) and R^(L03) may form a ring, each of R^(L01),R^(L02) and R^(L03) is a straight or branched alkylene group of 1 to 18carbon atoms when they form a ring; R^(L04) is a tertiary alkyl group of4 to 20 carbon atoms, a trialkylsilyl group in which each alkyl moietyhas 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or agroup of formula (L1); R^(L05) is a straight, branched or cyclic alkylgroup of 1 to 8 carbon atoms or a substituted or unsubstituted arylgroup of 6 to 20 carbon atoms; R^(L06) is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms or a substituted or unsubstitutedaryl group of 6 to 20 carbon atoms; R^(L07) to R^(L16) are independentlyhydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms whichmay contain a hetero atom, R^(L07) to R^(L16), taken together, may forma ring, and each of R^(L07) to R^(L16) represents a divalent hydrocarbongroup of 1 to 15 carbon atoms which may contain a hetero atom, when theyform a ring, or two of R^(L07) to R^(L16) which are attached toadjoining carbon atoms may bond together directly to form a double bond;y is an integer of 0 to 6, m is equal to 0 or 1, and n is equal to 0, 1,2 or 3, satisfying 2m+n=2 or 3.

A resist composition comprising the polymer defined above is alsoprovided.

In a further aspect, the invention provides a process for forming aresist pattern comprising the steps of applying the resist compositiondefined above onto a substrate to form a coating; heat treating thecoating and then exposing it to high-energy radiation or electron beamsthrough a photo mask; and optionally heat treating the exposed coatingand developing it with a developer.

The polymer comprising recurring units of formula (1) has the essentialunits introduced in a proportion x (referred to as x units,hereinafter), which characterize the overall properties of the polymer.More particularly, the x units are units having carboxylic acid coveredwith an acid-decomposable protective group, for providing a differentialdissolution rate between exposed and unexposed areas, which units aremore reactive with acid than prior art units. In general, a polymercontaining an alicyclic moiety in its backbone tends to blunt thereactivity of acid-decomposable protective groups with acid, probablybecause of the steric hindrance of the alicyclic moiety. In contrast,the x units used herein are capable of maintaining the reactivity at ahigh level since the acid-decomposable groups are introduced at a sitespaced apart from the alicyclic moiety. Additionally introducing ahighly polar group in the spacer moiety is effective for preventing thealicyclic backbone polymer from becoming excessively hydrophobic as isoften the case. Accordingly, the polymer comprising recurring units offormula (1) according to the invention possesses all together therigidity of the alicyclic backbone, the high reactivity ofacid-decomposable groups spaced apart from the backbone, and thehydrophilicity of highly polar groups introduced in the spacer moiety. Aresist composition using this polymer as a base resin is fully sensitiveto radiation even in a reduced dose, and leaves after development aprecisely configured micropattern firmly adhering to the substrate,which can maintain a sufficient thickness and satisfactory shape evenafter an etching step.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polymer

The polymer or high molecular weight compound of the invention isdefined as comprising units of the following general formula (1) andhaving a weight average molecular weight of 1,000 to 500,000.

In the above formula, k is equal to 0 or 1. Accordingly, the formula (1)can be represented by the following formulae (1-1) and (1-2) although itshould not be construed that a mixture of k=0 and k=1 is excluded.

Herein X is —CH₂— or —O—.

R¹ is hydrogen, methyl or CH₂CO₂R³. R² is hydrogen, methyl or CO₂R³. R³is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms.Examples of the straight, branched or cyclic C₁-C₁₅ alkyl groups includemethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl,butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl,ethyladamantyl, and butyladamantyl.

R⁴ is hydrogen, a straight, branched or cyclic alkyl group of 1 to 15carbon atoms, a straight, branched or cyclic alkoxyalkyl group of 2 to15 carbon atoms, or a straight, branched or cyclic acyl group of 1 to 15carbon atoms. Examples of the straight, branched or cyclic C₁-C₁₅ alkylgroups are as exemplified for R³. Examples of the straight, branched orcyclic C₂-C₁₅ alkoxyalkyl group include methoxymethyl, 1-ethoxyethyl,1-ethoxypropyl, 1-tert-butoxyethyl, 1-cyclohexyloxyethyl,2-tetrahydrofuranyl, and 2-tetrahydropyranyl. Examples of the straight,branched or cyclic C₁-C₁₅ acyl group include formyl, acetyl andpivaloyl.

R⁵ and R¹⁵ are acid labile groups.

At least one of R⁶ to R⁹ is a carboxyl or hydroxyl-containing monovalenthydrocarbon group of 1 to 15 carbon atoms (preferably straight, branchedor cyclic alkyl group), and the remainders are independently hydrogen ora straight, branched or cyclic alkyl group of 1 to 15 carbon atoms.Examples of the carboxyl or hydroxyl-containing monovalent hydrocarbongroup of 1 to 15 carbon atoms include carboxy, carboxymethyl,carboxyethyl, carboxybutyl, hydroxymethyl, hydroxyethyl, hydroxybutyl,2-carboxyethoxycarbonyl, 4-carboxybutoxycarbonyl,2-hydroxyethoxycarbonyl, 4-hydroxybutoxycarbonyl,carboxycyclopentyloxycarbonyl, carboxycyclohexyloxycarbonyl,carboxynorbornyloxycarbonyl, carboxyadamantyloxycarbonyl,hydroxycyclopentyloxycarbonyl, hydroxycyclohexyloxycarbonyl,hydroxynorbornyloxycarbonyl, and hydroxyadamantyloxycarbonyl. Examplesof the straight, branched or cyclic C₁-C₁₅ alkyl groups are asexemplified for R³. Alternatively, R⁶ to R⁹, taken together, form aring. When they form a ring, at least one of R⁶ to R⁹ is a carboxyl orhydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms(preferably straight, branched or cyclic alkylene group), and theremainders are independently a single bond or a straight, branched orcyclic alkylene group of 1 to 15 carbon atoms. Examples of the carboxylor hydroxyl-containing divalent C₁-C₁₅ hydrocarbon group are thoseexemplified for the carboxyl or hydroxyl-containing monovalenthydrocarbon group, with one hydrogen atom being eliminated therefrom.Examples of the straight, branched or cyclic C₁-C₁₅ alkylene group arethose exemplified for R³, with one hydrogen atom being eliminatedtherefrom.

At least one of R¹⁰ to R¹³ is a monovalent hydrocarbon group of 2 to 15carbon atoms containing a —CO₂— partial structure, and the remaindersare independently hydrogen or a straight, branched or cyclic alkyl groupof 1 to 15 carbon atoms. Examples of the monovalent C₂-C₁₅ hydrocarbongroup containing a —CO₂— partial structure include2-oxooxolan-3-yloxycarbonyl, 4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic C₁-C₁₅ alkyl group are as exemplified for R³. Alternatively,R¹⁰ to R¹³, taken together, form a ring. When they form a ring, at leastone of R¹⁰ to R¹³ is a divalent hydrocarbon group of 1 to 15 carbonatoms containing a —CO₂— partial structure, and the remainders areindependently a single bond or a straight, branched or cyclic alkylenegroup of 1 to 15 carbon atoms. Examples of the divalent C₁-C₁₅hydrocarbon group containing a —CO₂— partial structure include1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl as wellas those exemplified above for the monovalent hydrocarbon groupcontaining a —CO₂— partial structure, with one hydrogen atom beingeliminated therefrom. Examples of the straight, branched or cyclicC₁-C₁₅ alkylene group are those exemplified for R³, with one hydrogenatom being eliminated therefrom.

R¹⁴ is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or analkyl group containing such a polycyclic hydrocarbon group. Examplesinclude norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl,adamantyl, ethyladamantyl, butyladamantyl, norbornylmethyl, andadamantylmethyl.

Z is a trivalent hydrocarbon group of 1 to 10 carbon atoms, examples ofwhich include methine, ethane-1,1,1-triyl, ethane-1,1,2-triyl,propane-1,2,2-triyl, propane-1,3,3-triyl, butane-1,2,2-triyl, andbutane-1,4,4-triyl. Alternatively, Z forms a ring with R¹, and in thisevent, R¹ is methylene and Z is a tetravalent hydrocarbon group of 1 to10 carbon atoms, examples of which are propane-1,1,1,3-tetrayl andbutane-1,1,1,4-tetrayl.

Subscript x is a number of more than 0, preferably from 0.2 to 0.9, morepreferably from 0.3 to 0.8; and a, b, c and d are 0 or positive numbers,preferably from 0 to 0.6, and more preferably from 0 to 0.4. The sum ofthese subscripts, x+a+b+c+d is equal to 1.

The acid labile groups represented by R⁵ and R¹⁵ may be selected from avariety of such groups. Examples of the acid labile group are groups ofthe following general formulae (L1) to (L4), tertiary alkyl groups of 4to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilylgroups in which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkylgroups of 4 to 20 carbon atoms.

R^(L01) and R^(L02) are hydrogen or straight, branched or cyclic alkylgroups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms.Exemplary alkyl groups include methyl, ethyl, propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl,and n-octyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbonatoms, preferably 1 to 10 carbon atoms, which may contain a hetero atomsuch as oxygen, examples of which include unsubstituted straight,branched or cyclic alkyl groups and straight, branched or cyclic alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples are thesubstituted alkyl groups shown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may form a ring. Each of R^(L01), R^(L02) and R^(L03) is astraight or branched alkylene group of 1 to 18 carbon atoms, preferably1 to 10 carbon atoms when they form a ring.

R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4to 15 carbon atoms, a trialkylsilyl group in which each alkyl moiety has1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or agroup of formula (L1). Exemplary tertiary alkyl groups are tert-butyl,tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl,1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl,1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Exemplarytrialkylsilyl groups are trimethylsilyl, triethylsilyl, anddimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl,4-methyl-2-oxooxan-4-yl, and 5-methyl-5-oxooxolan-4-yl. Letter y is aninteger of 0 to 6.

R^(L05) is a straight, branched or cyclic alkyl group of 1 to 8 carbonatoms or a substituted or unsubstituted aryl group of 6 to 20 carbonatoms. Examples of the straight, branched or cyclic alkyl group includemethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl,cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl, andcyclohexylethyl. Exemplary aryl groups are phenyl, methylphenyl,naphthyl, anthryl, phenanthryl, and pyrenyl. Letter m is equal to 0 or1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or 3.

R^(L06) is a straight, branched or cyclic alkyl group of 1 to 8 carbonatoms or a substituted or unsubstituted aryl group of 6 to 20 carbonatoms. Examples of these groups are the same as exemplified for R^(L05).

R^(L07) to R^(L16) independently represent hydrogen or monovalenthydrocarbon groups of 1 to 15 carbon atoms which may contain a heteroatom. Exemplary hydrocarbon groups are straight, branched or cyclicalkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl,n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl,cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl,and substituted ones of these groups in which some hydrogen atoms arereplaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino,alkylamino, cyano, mercapto, alkylthio, sulfo or other groups.Alternatively, R^(L07) to R^(L16), taken together, form a ring (forexample, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09), R^(L08) andR^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12), R^(L13) and R^(L14),or a similar pair form a ring). Each of R^(L07) to R^(L16) represents adivalent C₁-C₁₅ hydrocarbon group which may contain a hetero atom, whenthey form a ring, examples of which are the ones exemplified above forthe monovalent hydrocarbon groups, with one hydrogen atom beingeliminated. Two of R^(L07) to R^(L16) which are attached to adjoiningcarbon atoms (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair) may bond togetherdirectly to form a double bond.

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyl-oxycarbonylmethyl,1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxy-carbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butyl-cyclopentyl, 1-sec-butylcyclopentyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

The acid labile groups of formula (L4) are exemplified by the followinggroups.

Examples of the tertiary alkyl, trialkylsilyl and oxoalkyl groupsincluded in the acid labile groups represented by R⁵ and R¹⁵ are asexemplified above.

As the acid labile group represented by R⁵ or R¹⁵, there may be used onetype or a combination of two or more types. The use of acid labilegroups of different types enables fine adjustment of a pattern profile.

In preparing the polymer comprising recurring units of formula (1)according to the invention, copolymerization reaction is effected usinga compound of the following general formula (2) as a first monomer andat least one compound of the following general formulae (3) to (6) as asecond monomer and subsequent monomer(s).

Herein R¹ to R¹⁵, Z, X and k are as defined above.

It is understood that when Z is CHCH₂, for example, the monomer offormula (2) can be prepared according to the following scheme.

Herein R¹ to R⁵, Z and X are as defined above, and R^(4′) is a precursorfor protecting a hydroxyl group to form —OR⁴.

Copolymerization reaction is carried out by mixing the compound offormula (2) with at least one compound selected from the compounds offormulae (3) to (6) in an appropriate proportion, determined by takinginto account a reactivity, optionally dissolving them in a solvent, andadding a suitable polymerization initiator or catalyst. Then reaction iscarried out at a suitable temperature for a suitable time. Althoughvarious modes are available for copolymerization reaction, coordinationpolymerization is but one exemplary mode.

For coordination polymerization, preferred reaction conditions include(a) a solvent selected from among hydrocarbons such as n-heptane andtoluene, (b) a catalyst selected from Ziegler-Natta catalysts comprisinga transition metal (e.g., titanium) and alkyl aluminum, Phillipscatalysts of metal oxides having chromium or nickel compounds carriedthereon, and olefin-metathesis mixed catalysts as typified by tungstenand rhenium mixed catalysts, (c) a temperature of about 0° C. to about100° C., and (d) a time of about ½ hour to about 48 hours. Reactionconditions outside the described range may be employed if desired.

In the copolymerization reaction, the amounts of the respective monomersare adjusted so that the resulting polymer may provide optimumperformance when formulated as a resist composition.

The polymers comprising recurring units of formula (1) according to theinvention have a weight average molecular weight of 1,000 to 500,000,preferably 3,000 to 100,000. Outside the range, the etching resistancemay become extremely low and the resolution may become low because asubstantial difference in dissolution rate before and after exposure islost.

Resist composition

The invention also provides a resist composition comprising the polymerhaving units of formula (1) as a base resin.

In addition to the polymer having units of formula (1), the resistcomposition of the invention may contain a photoacid generator and anorganic solvent.

Photoacid Generator

The photoacid generator is a compound capable of generating an acid uponexposure to high energy radiation or electron beams and includes thefollowing:

(i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),

(ii) diazomethane derivatives of the formula (P2),

(iii) glyoxime derivatives of the formula (P3),

(iv) bissulfone derivatives of the formula (P4),

(v) sulfonic acid esters of N-hydroxyimide compounds of the formula(P5),

(vi) β-ketosulfonic acid derivatives,

(vii) disulfone derivatives,

(viii) nitrobenzylsulfonate derivatives, and

(ix) sulfonate derivatives.

These photoacid generators are described in detail.

(i) Onium salts of formula (P1a-1), (P1a-2) or (P1b):

Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are alkylene groups of 1 to 6 carbon atoms when theyform a ring. K⁻ is a non-nucleophilic counter ion.

R^(101a), R^(101b), and R^(101c) may be the same or different and areillustrated below. Exemplary alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary aryl groups include phenyland naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K⁻ include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

Herein, R^(102a) and R^(102b) independently represent straight, branchedor cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ represents astraight, branched or cyclic alkylene groups of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

Illustrative of the groups represented by R^(102a) and R^(102b) aremethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

(ii) Diazomethane derivatives of formula (P2)

Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branched orcyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, arylor halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of7 to 12 carbon atoms.

Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkyl groupsinclude methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

(iii) Glyoxime derivatives of formula (P3)

Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, taken together, mayform a ring. R¹⁰⁸ and R¹⁰⁹ each are straight or branched alkylene groupsof 1 to 6 carbon atoms when they form a ring.

Illustrative examples of the alkyl, halogenated alkyl, aryl, halogenatedaryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ are thesame as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of the alkylene groupsrepresented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene, propylene,butylene, and hexylene.

(iv) Bissulfone derivatives of formula (P4)

Herein, R^(101a) and R^(101b) are as defined above.

(v) Sulfonic acid esters of N-hydroxyimide compounds of formula (P5)

Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms, alkylene groupof 1 to 6 carbon atoms, or alkenylene group of 2 to 6 carbon atomswherein some or all of the hydrogen atoms may be replaced by straight orbranched alkyl or alkoxy groups of 1 to 4 carbon atoms, nitro, acetyl,or phenyl groups. R¹¹¹ is a straight, branched or cyclic alkyl group of1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl or naphthyl groupwherein some or all of the hydrogen atoms may be replaced by alkyl oralkoxy groups of 1 to 4 carbon atoms, phenyl groups (which may havesubstituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, oracetyl group), hetero-aromatic groups of 3 to 5 carbon atoms, orchlorine or fluorine atoms.

Of the groups represented by R¹¹⁰, exemplary arylene groups include1,2-phenylene and 1,8-naphthylene; exemplary alkylene groups includemethylene, 1,2-ethylene, 1,3-propylene, 1,4-butylene,1-phenyl-1,2-ethylene, and norbornane-2,3-diyl; and exemplary alkenylenegroups include 1,2-vinylene, 1-phenyl-1,2-vinylene, and5-norbornene-2,3-diyl. Of the groups represented by R¹¹¹, exemplaryalkyl groups are as exemplified for R^(101a) to R^(101c); exemplaryalkenyl groups include vinyl, 1-propenyl, allyl, 1-butenyl, 3-butenyl,isoprenyl, 1-pentenyl, 3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl,3-hexenyl, 5-hexenyl, 1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl;and exemplary alkoxyalkyl groups include methoxymethyl, ethoxymethyl,propoxymethyl, butoxymethyl, pentyloxymethyl, hexyloxymethyl,heptyloxymethyl, methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl,pentyloxyethyl, hexyloxyethyl, methoxypropyl, ethoxypropyl,propoxypropyl, butoxypropyl, methoxybutyl, ethoxybutyl, propoxybutyl,methoxypentyl, ethoxypentyl, methoxyhexyl, and methoxyheptyl.

Of the substituents on these groups, the alkyl groups of 1 to 4 carbonatoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl andtert-butyl; the alkoxy groups of 1 to 4 carbon atoms include methoxy,ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, and tert-butoxy; thephenyl groups which may have substituted thereon an alkyl or alkoxy of 1to 4 carbon atoms, nitro, or acetyl group include phenyl, tolyl,p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl; thehetero-aromatic groups of 3 to 5 carbon atoms include pyridyl and furyl.

Illustrative examples of the photoacid generator include:

onium salts such as diphenyliodonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,diphenyliodonium p-toluene-sulfonate,(p-tert-butoxyphenyl)phenyliodonium p-toluene-sulfonate,triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethane-sulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,triphenylsulfonium nonafluorobutanesulfonate, triphenylsulfoniumbutanesulfonate, trimethylsulfonium trifluoromethanesulfonate,trimethylsulfonium p-toluenesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,dimethylphenylsulfonium trifluoromethanesulfonate,dimethylphenylsulfonium p-toluenesulfonate, dicyclohexylphenylsulfoniumtrifluoromethanesulfonate, dicyclohexylphenylsulfoniump-toluenesulfonate, trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocyclo-hexyl)sulfoniumtrifluoromethanesulfonate,ethylenebis-[methyl(2-oxocyclopentyl)sulfoniumtrifluoromethane-sulfonate], and1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane, bis(xylenesulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(cyclopentylsulfonyl)diazomethane, bis(n-butylsulfonyl)diazomethane,bis(isobutylsulfonyl)diazomethane, bis(sec-butylsulfonyl)diazomethane,bis(n-propylsulfonyl)diazomethane, bis(isopropylsulfonyl)diazomethane,bis(tert-butylsulfonyl)diazomethane, bis(n-amylsulfonyl)diazomethane,bis(isoamylsulfonyl)diazomethane, bis(sec-amylsulfonyl)diazomethane,bis(tert-amylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such asbis-o-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-o-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-o-(p-toluenesulfonyl)-α-dicyclohexyl-glyoxime,bis-o-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-o-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-α-dimethylglyoxime,bis-o-(n-butanesulfonyl)-α-diphenylglyoxime,bis-o-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-o-(n-butane-sulfonyl)-2,3-pentanedioneglyoxime,bis-o-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,bis-o-(methanesulfonyl)-α-dimethylglyoxime,bis-o-(trifluoro-methanesulfonyl)-α-dimethylglyoxime,bis-o-(1,1,1-trifluoro-ethanesulfonyl)-α-dimethylglyoxime,bis-o-(tert-butanesulfonyl)-α-dimethylglyoxime,bis-o-(perfluorooctanesulfonyl)-α-dimethylglyoxime,bis-o-(cyclohexanesulfonyl)-α-dimethylglyoxime,bis-o-(benzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-o-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,bis-o-(xylenesulfonyl)-α-dimethylglyoxime, andbis-o-(camphorsulfonyl)-α-dimethylglyoxime;

bissulfone derivatives such as bisnaphthylsulfonylmethane,bistrifluoromethylsulfonylmethane, bismethylsulfonylmethane,bisethylsulfonylmethane, bispropylsulfonylmethane,bisisopropylsulfonylmethane, bis-p-toluenesulfonylmethane, andbisbenzenesulfonylmethane;

β-ketosulfone derivatives such as2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

disulfone derivatives such as diphenyl disulfone and dicyclohexyldisulfone;

nitrobenzyl sulfonate derivatives such as 2,6-dinitrobenzylp-toluenesulfonate and 2,4-dinitrobenzyl p-toluenesulfonate;

sulfonic acid ester derivatives such as1,2,3-tris-(methanesulfonyloxy)benzene,1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and1,2,3-tris(p-toluenesulfonyloxy)benzene; and

sulfonic acid esters of N-hydroxyimides such as N-hydroxysuccinimidemethanesulfonate, N-hydroxysuccinimide trifluoromethanesulfonate,N-hydroxysuccinimide ethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimide1-octanesulfonate, N-hydroxysuccinimide p-toluenesulfonate,N-hydroxysuccinimide p-methoxybenzenesulfonate, N-hydroxysuccinimide2-chloroethanesulfonate, N-hydroxysuccinimide benzenesulfonate,N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,N-hydroxysuccinimide 1-naphthalenesulfonate, N-hydroxysuccinimide2-naphthalenesulfonate, N-hydroxy-2-phenylsuccinimide methanesulfonate,N-hydroxy-maleimide methanesulfonate, N-hydroxymaleimideethanesulfonate, N-hydroxy-2-phenylmaleimide methanesulfonate,N-hydroxyglutarimide methanesulfonate, N-hydroxyglutarimidebenzenesulfonate, N-hydroxyphthalimide methanesulfonate,N-hydroxyphthalimide benzenesulfonate, N-hydroxyphthalimidetrifluoromethanesulfonate, N-hydroxyphthalimide p-toluenesulfonate,N-hydroxynaphthalimide methanesulfonate, N-hydroxynaphthalimidebenzenesulfonate, N-hydroxy-5-norbornene-2,3-dicarboxyimidemethanesulfonate, N-hydroxy-5-norbornene-2,3-dicarboxyimidetrifluoromethanesulfonate, and N-hydroxy-5-norbornene-2,3-dicarboxyimidep-toluenesulfonate.

Preferred among these photoacid generators are onium salts such astriphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,triphenylsulfonium p-toluenesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,trinaphthylsulfonium trifluoromethanesulfonate,cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethanesulfonate,(2-norbornyl)methyl(2-oxocylohexyl)sulfonium trifluoromethanesulfonate,and 1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;diazomethane derivatives such as bis(benzenesulfonyl)diazomethane,bis(p-toluenesulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane,bis(n-butylsulfonyl)diazomethane, bis(isobutylsulfonyl)diazomethane,bis(sec-butylsulfonyl)diazomethane, bis(n-propylsulfonyl)diazomethane,bis(isopropylsulfonyl)diazomethane, andbis(tert-butylsulfonyl)diazomethane; glyoxime derivatives such asbis-o-(p-toluenesulfonyl)-α-dimethylglyoxime andbis-o-(n-butanesulfonyl)-α-dimethylglyoxime; bissulfone derivatives suchas bisnaphthylsulfonylmethane; and sulfonic acid esters ofN-hydroxyimide compounds such as N-hydroxysuccinimide methanesulfonate,N-hydroxysuccinimide trifluoromethanesulfonate, N-hydroxysuccinimide1-propanesulfonate, N-hydroxysuccinimide 2-propanesulfonate,N-hydroxysuccinimide 1-pentanesulfonate, N-hydroxysuccinimidep-toluenesulfonate, N-hydroxynaphthalimide methanesulfonate, andN-hydroxynaphthalimide benzenesulfonate.

These photoacid generators may be used singly or in combinations of twoor more thereof. Onium salts are effective for improving rectangularity,while diazomethane derivatives and glyoxime derivatives are effectivefor reducing standing waves. The combination of an onium salt with adiazomethane or a glyoxime derivative allows for fine adjustment of theprofile.

The photoacid generator is added in an amount of 0.1 to 15 parts, andespecially 0.5 to 8 parts by weight, per 100 parts by weight of the baseresin (all parts are by weight, hereinafter). Less than 0.1 part of thephotoacid generator would provide a poor sensitivity whereas more than15 parts of the photoacid generator would adversely affect transparencyand resolution.

Organic Solvent

The organic solvent used herein may be any organic solvent in which thebase resin, photoacid generator, and other components are soluble.Illustrative, non-limiting, examples of the organic solvent includeketones such as cyclohexanone and methyl-2-n-amylketone; alcohols suchas 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,and diethylene glycol dimethyl ether; and esters such as propyleneglycol monomethyl ether acetate, propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate. These solvents may be used alone or in combinations of two ormore thereof. Of the above organic solvents, it is recommended to usediethylene glycol dimethyl ether and 1-ethoxy-2-propanol because thephotoacid generator serving as one of the resist components is mostsoluble therein, propylene glycol monomethyl ether acetate because it isa safe solvent, or a mixture thereof.

An appropriate amount of the organic solvent used is about 200 to 1,000parts, especially about 400 to 800 parts by weight per 100 parts byweight of the base resin.

Other Polymer

To the resist composition of the invention, another polymer other thanthe inventive polymer may also be added. The other polymers that can beadded to the resist composition are, for example, those polymerscomprising units of the following formula (R1) or (R2) and having aweight average molecular weight of about 1,000 to about 500,000,especially about 5,000 to about 100,000 although the other polymers arenot limited thereto.

Herein, R⁰⁰¹ is hydrogen, methyl or CH₂CO₂R⁰⁰³. R⁰⁰² is hydrogen, methylor CO₂R⁰⁰³. R⁰⁰³ is a straight, branched or cyclic alkyl group of 1 to15 carbon atoms. R⁰⁰⁴ is hydrogen or a monovalent hydrocarbon group of 1to 15 carbon atoms having a carboxyl or hydroxyl group. At least one ofR⁰⁰⁵ to R⁰⁰⁸ represents a monovalent hydrocarbon group of 1 to 15 carbonatoms having a carboxyl or hydroxyl group while the remaining R'sindependently represent hydrogen or a straight, branched or cyclic alkylgroup of 1 to 15 carbon atoms. Alternatively, R⁰⁰⁵ to R⁰⁰⁸, takentogether, may form a ring, and in that event, at least one of R⁰⁰⁵ toR⁰⁰⁸ is a divalent hydrocarbon group of 1 to 15 carbon atoms having acarboxyl or hydroxyl group, while the remaining R's are independentlysingle bonds or straight, branched or cyclic alkylene groups of 1 to 15carbon atoms. R⁰⁰⁹ is a monovalent hydrocarbon group of 3 to 15 carbonatoms containing a —CO₂— partial structure. At least one of R⁰¹⁰ to R⁰¹³is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a—CO₂— partial structure, while the remaining R's are independentlyhydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbonatoms. R⁰¹⁰ to R⁰¹³, taken together, may form a ring, and in that event,at least one of R⁰¹⁰ to R⁰¹³ is a divalent hydrocarbon group of 1 to 15carbon atoms containing a —CO₂— partial structure, while the remainingR's are independently single bonds or straight, branched or cyclicalkylene groups of 1 to 15 carbon atoms. R⁰¹⁴ is a polycyclichydrocarbon group having 7 to 15 carbon atoms or an alkyl groupcontaining a polycyclic hydrocarbon group. R⁰¹⁵ is an acid labile group.R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight, branched or cyclic alkylgroup of 1 to 8 carbon atoms. X is methylene or an oxygen atom. Letterk′ is equal to 0 or 1; a1′, a2′, a3′, b1′, b2′, b3′, c1′, c2′, c3′, d1′,d2′, d3′, and e′ are numbers from 0 to less than 1, satisfying

a1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1; f′, g′, h′, i′,and j′ are numbers from 0 to less than 1, satisfying f′+g′+h′+i′+j′=1.Illustrative examples of the respective groups are the same asexemplified for R¹ to R¹⁵.

The inventive polymer (polymer having units of formula (1)) and theother polymer are preferably blended in a weight ratio from 10:90 to90:10, more preferably from 20:80 to 80:20. If the blend ratio of theinventive polymer is below this range, the resist composition wouldbecome poor in some of the desired properties. The properties of theresist composition can be adjusted by properly changing the blend ratioof the inventive polymer.

The other polymer is not limited to one type and a mixture of two ormore other polymers may be added. The use of plural polymers allows foreasy adjustment of resist properties.

Dissolution Regulator

To the resist composition, a dissolution regulator may be added. Thedissolution regulator is a compound having on the molecule at least twophenolic hydroxyl groups, in which an average of from 0 to 100 mol % ofall the hydrogen atoms on the phenolic hydroxyl groups are replaced withacid labile groups or a compound having on the molecule at least onecarboxyl group, in which an average of 50 to 100 mol % of all thehydrogen atoms on the carboxyl groups are replaced with acid labilegroups, both the compounds having an average molecular weight within arange of 100 to 1,000, and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched alkyl or alkenyl of 1 to 8 carbon atoms; R²⁰³ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or—(R²⁰⁷)_(h)—COOH; R²⁰⁴ is —(CH₂)_(i)— (where i=2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R²⁰⁵ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straightor branched alkylene of 1 to 10 carbon atoms; R²⁰⁸ is hydrogen orhydroxyl; the letter j is an integer from 0 to 5; u and h are each 0 or1; s, t, s′, t′, s″, and t″ are each numbers which satisfy s+t=8,s′+t′=5, and s″+t″=4, and are such that each phenyl skeleton has atleast one hydroxyl group; and α is a number such that the compounds offormula (D8) or (D9) have a molecular weight of from 100 to 1,000.

In the above formulas, suitable examples of R²⁰¹ and R²⁰² includehydrogen, methyl, ethyl, butyl, propyl, ethynyl, and cyclohexyl;suitable examples of R²⁰³ include the same groups as for R²⁰¹ and R²⁰²,as well as —COOH and —CH₂COOH; suitable examples of R²⁰⁴ includeethylene, phenylene, carbonyl, sulfonyl, oxygen, and sulfur; suitableexamples of R²⁰⁵ include methylene as well as the same groups as forR²⁰⁴; and suitable examples of R²⁰⁶ include hydrogen, methyl, ethyl,butyl, propyl, ethynyl, cyclohexyl, and hydroxyl-substituted phenyl ornaphthyl.

Exemplary acid labile groups on the dissolution regulator include groupsof the following general formulae (L1) to (L4), tertiary alkyl groups of4 to 20 carbon atoms, trialkylsilyl groups in which each of the alkylshas 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms.

In these formulas, R^(L01) and R^(L02) are each hydrogen or a straight,branched or cyclic alkyl having 1 to 18 carbon atoms; and R^(L03) is amonovalent hydrocarbon group of 1 to 18 carbon atoms which may contain aheteroatom (e.g., oxygen). A pair of R^(L01) and R^(L02) a pair ofR^(L01) and R^(L03), or a pair of R^(L02) and R^(L03) may together forma ring, with the proviso that R^(L01), R^(L02), and R^(L03) are each astraight or branched alkylene of 1 to 18 carbon atoms when they form aring. R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms, atrialkysilyl group in which each of the alkyls has 1 to 6 carbon atoms,an oxoalkyl group of 4 to 20 carbon atoms, or a group of the formula(L1). R^(L05) is a straight, branched or cyclic alkyl group of 1 to 8carbon atoms or a substituted or unsubstituted aryl group of 6 to 20carbon atoms. R^(L06) is a straight, branched or cyclic alkyl group of 1to 8 carbon atoms or a substituted or unsubstituted aryl group of 6 to20 carbon atoms. R^(L07) to R^(L16) independently represent hydrogen ormonovalent hydrocarbon groups of 1 to 15 carbon atoms which may containa hetero atom. Alternatively, R^(L07) to R^(L16), taken together, mayform a ring. Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅hydrocarbon group which may contain a hetero atom, when they form aring. Two of R^(L07) to R^(L16) which are attached to adjoining carbonatoms may bond together directly to form a double bond. Letter y is aninteger of 0 to 6. Letter m is equal to 0 or 1, n is equal to 0, 1, 2 or3, and 2m+n is equal to 2 or 3.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 5 to 50 parts, and more preferably 10 to 30 parts, per100 parts of the base resin, and may be used singly or as a mixture oftwo or more thereof. Less than 5 parts of the dissolution regulator mayfail to yield an improved resolution, whereas the use of more than 50parts would lead to slimming of the patterned film, and thus a declinein resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

Basic Compound

In the resist composition of the invention, a basic compound may beblended. A suitable basic compound used herein is a compound capable ofsuppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

Examples of basic compounds include primary, secondary, and tertiaryaliphatic amines, mixed amines, aromatic amines, heterocyclic amines,carboxyl group-bearing nitrogenous compounds, sulfonyl group-bearingnitrogenous compounds, hydroxyl group-bearing nitrogenous compounds,hydroxyphenyl group-bearing nitrogenous compounds, alcoholic nitrogenouscompounds, amide derivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-isopropylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyl-tetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,1-methyl-2-pyridine, 4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable carboxyl group-bearing nitrogenous compoundsinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable sulfonyl group-bearing nitrogenous compounds include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable hydroxyl group-bearing nitrogenous compounds, hydroxyphenylgroup-bearing nitrogenous compounds, and alcoholic nitrogenous compoundsinclude 2-hydroxypyridine, aminocresol, 2,4-quinolinediol,3-indolemethanol hydrate, monoethanolamine, diethanolamine,triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine,truisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol,3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]-piperazine, piperidine ethanol,1-(2-hydroxyethyl)-pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)-isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

In addition, basic compounds of the following general formula (Bl) mayalso be included alone or in admixture.

N(X)_(n)(Y)_(3−n)  B1

In the formula, n is equal to 1, 2 or 3; Y is independently hydrogen ora straight, branched or cyclic alkyl group of 1 to 20 carbon atoms whichmay contain a hydroxyl group or ether; and X is independently selectedfrom groups of the following general formulas (X1) to (X3), and two orthree X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl group,ether, ester or lactone ring; and R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms.

Illustrative examples of the compounds of formula (B1) includetris(2-methoxymethoxyethyl)amine, tris{2-(methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxy-methoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris(2-(1-ethoxy-propoxy)ethylamine,tris[2-{2-(2-hydroxyethoxy)ethoxy}-ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo-[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo-[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine,N,N-bis(2-methoxyethyl)-2-(2-methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxy-carbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxy-carbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

The basic compound is preferably formulated in an amount of 0.001 to 10parts, and especially 0.01 to 1 part, per part of the photoacidgenerator. Less than 0.001 part of the basic compound fails to achievethe desired effects thereof, while the use of more than 10 parts wouldresult in too low a sensitivity and resolution.

Other Components

In the resist composition, a compound bearing a ≡C—COOH group in amolecule may be blended. Exemplary, non-limiting compounds bearing a≡C—COOH group include one or more compounds selected from Groups I andII below. Including this compound improves the PED stability of theresist and ameliorates edge roughness on nitride film substrates.

Group I:

Compounds in which some or all of the hydrogen atoms on the phenolichydroxyl groups of the compounds of general formulas (A1) to (A10) belowhave been replaced with —R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight orbranched alkylene of 1 to 10 carbon atoms), and in which the molar ratioC/(C+D) of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in themolecule is from 0.1 to 1.0.

[Group I]

In these formulas, R⁴⁰⁸ is hydrogen or methyl; R⁴⁰² and R⁴⁰³ are eachhydrogen or a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms; R⁴⁰⁴ is hydrogen, a straight or branched alkyl or alkenyl of 1 to8 carbon atoms, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogen or—R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), an arylene of 6to 10 carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfuratom; R⁴⁰⁶ is an alkylene of 1 to 10 carbon atoms, an arylene of 6 to 10carbon atoms, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁷is hydrogen, a straight or branched alkyl or alkenyl of 1 to 8 carbonatoms, or a hydroxyl-substituted phenyl or naphthyl; R⁴⁰⁹ is a straightor branched alkylene of 1 to 10 carbon atoms; R⁴¹⁰ is hydrogen, astraight or branched alkyl or alkenyl of 1 to 8 carbon atoms, or a—R⁴¹¹—COOH group; R⁴¹¹ is a straight or branched alkylene of 1 to 10carbon atoms; the letter j is an integer from 0 to 5; u and h are each 0or 1; s1, t1, s2, t2, s3, t3, s4, and t4 are each numbers which satisfys1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6, and are such that each phenylskeleton has at least one hydroxyl group; κ is a number such that thecompound of formula (A6) may have a weight average molecular weight of1,000 to 5,000; and λ is a number such that the compound of formula (A7)may have a weight average molecular weight of 1,000 to 10,000.

Group II:

Compounds of general formulas (A11) to (A15) below.

[Group II]

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R⁴¹² ishydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0, t5≧0,and s5+t5=5; and h′ is equal to 0 or 1.

Illustrative, non-limiting examples of the compound bearing a ≡C—COOHgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a CH₂COOH group such that theCH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, α andK are as defined above.

The compound bearing a ≡C—COOH group within the molecule may be usedsingly or as combinations of two or more thereof.

The compound bearing a ≡C—COOH group within the molecule is added in anamount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, morepreferably 0.1 to 3 parts, further preferably 0.1 to 2 parts, per 100parts of the base resin. More than 5 parts of the compound can reducethe resolution of the resist composition.

The resist composition of the invention may additionally include anacetylene alcohol derivative for the purpose of enhancing the shelfstability. Preferred acetylene alcohol derivatives are those having thegeneral formula (S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched, or cyclic alkyl of 1 to 8 carbon atoms; and X and Yare each 0 or a positive number, satisfying 0≦X≦30, 0≦Y≦30, and0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industry K. K.

The acetylene alcohol derivative is preferably added in an amount of0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, per 100%by weight of the resist composition. Less than 0.01% by weight would beineffective for improving coating characteristics and shelf stability,whereas more than 2% by weight would result in a resist having a lowresolution.

The resist composition of the invention may include, as an optionalingredient, a surfactant which is commonly used for improving thecoating characteristics. Optional ingredients may be added inconventional amounts so long as this does not compromise the objects ofthe invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Florade FC-430 and FC-431from Sumitomo 3M K. K., Surflon S-141 and S-145 from Asahi Glass K. K.,Unidine DS-401, DS-403 and DS-451 from Daikin Industry K. K., MegafaceF-8151 from Dai-Nippon Ink & Chemicals K. K., and X-70-092 and X-70-093from Shin-Etsu Chemical Co., Ltd. Preferred surfactants are FloradeFC-430 from Sumitomo 3M K. K. and X-70-093 from Shin-Etsu Chemical Co.,Ltd.

Pattern formation using the resist composition of the invention may becarried out by a known lithographic technique. For example, the resistcomposition is applied onto a substrate such as a silicon wafer by spincoating or the like to form a resist film having a thickness of 0.3 to2.0 μm, which is then pre-baked on a hot plate at 60 to 150° C. for 1 to10 minutes, and preferably at 80 to 130° C. for 1 to 5 minutes. Apatterning mask having the desired pattern is then placed over theresist film, and the film exposed through the mask to an electron beamor to high-energy radiation such as deep-UV rays, an excimer laser, orx-rays in a dose of about 1 to 200 mJ/cm², and preferably about 10 to100 mJ/cm², then post-exposure baked (PEB) on a hot plate at 60 to 150°C. for 1 to 5 minutes, and preferably at 80 to 130° C. for 1 to 3minutes. Finally, development is carried out using as the developer anaqueous alkali solution, such as a 0.1 to 5% (preferably 2 to 3%)aqueous solution of tetramethylammonium hydroxide (TMAH), this beingdone by a conventional method such as dipping, puddling, or spraying fora period of 0.1 to 3 minutes, and preferably 0.5 to 2 minutes. Thesesteps result in the formation of the desired pattern on the substrate.Of the various types of high-energy radiation that may be used, theresist composition of the invention is best suited to fine patternformation with, in particular, deep-UV rays having a wavelength of 248to 193 nm, an excimer laser, x-rays, or an electron beam. The desiredpattern may not be obtainable outside the upper and lower limits of theabove range.

The resist composition comprising the polymer of the invention as a baseresin lends itself to micropatterning with electron beams or deep-UWrays since it is sensitive to high-energy radiation and has excellentsensitivity, resolution, and etching resistance. Especially because ofthe minimized absorption at the exposure wavelength of an ArF or KrFexcimer laser, a finely defined pattern having sidewalls perpendicularto the substrate can easily be formed.

EXAMPLE

Synthesis Examples and Examples are given below together withComparative Examples for further illustrating the invention although theinvention is not limited thereto.

Synthesis Examples

The polymers used in Examples and Comparative Examples were synthesizedusing monomers designated Monomers 1 to 8.

It is noted that Monomer 1 was synthesized by reactingtetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-ene-8-carbaldehyde withtert-butyl acetate in the presence of lithium hexamethyldisilazide.Monomers 2 to 5 were synthesized by a similar process or using a similarorganic chemical formulation.

Synthesis Example 1

Synthesis of Polymer 1

In a nitrogen atmosphere, 15.2 g of Monomer 1 and 8.4 g of Monomer 6were dissolved in 500 ml of tetrahydrofuran, to which 0.7 g of acatalyst Mo(N-2,6-C₆H₃Pr^(i) ₂)(CHCMe₃)(OBu^(t))₂ was added, followed bystirring. After one hour of reaction at room temperature, 0.7 g ofbutanal was added to the reaction mixture, which was stirred for afurther 30 minutes. The reaction mixture, to which 1.5 g of1,3-diaminopropane was added, was heated to 80° C. and stirred for onehour under a hydrogen partial pressure of 0.5 MPa. The reaction solutionwas added dropwise to 10 liters of methanol. The resulting solids werecollected by filtration, washed with 10 liters of methanol, and dried invacuum at 60° C. for 12 hours. The solids were dissolved in 1.5 litersof tetrahydrofuran again. A catalytic amount of rutheniumdichlorotetrakis(triphenylphosphine) and triethylamine was added to thesolution, which was heated to 160° C. and stirred for 6 hours under ahydrogen partial pressure of 8 MPa. The hydrogen was released, and thereaction mixture was cooled to room temperature. The reaction mixturewas added dropwise to 10 liters of methanol. The resulting solids werecollected by filtration, washed with 10 liters of methanol, and dried invacuum at 60° C. for 12 hours, obtaining 19.8 g of a polymer, designatedPolymer 1. The yield was 83.9%.

Synthesis Examples 2 to 8

Synthesis of Polymers 2 to 8

Polymers 2 to 8 were synthesized by the same procedure as above or by awell-known method.

Example I

Resist compositions were formulated using inventive polymers andexamined for resolution upon KrF excimer laser exposure.

Examples I-1 to I-16

Evaluation of Resist Resolution

Resist compositions were prepared by using Polymers 1 to 6 as the baseresin, and dissolving the polymer, a photoacid generator (designated asPAG 1 and 2), a dissolution regulator (designated as DRR 1 to 4), abasic compound, and a compound having a ≡C—COOH group in the molecule(ACC 1 and 2) in a solvent in accordance with the formulation shown inTable 1. These compositions were each filtered through a Teflon filter(pore diameter 0.2 μm), thereby giving resist solutions.

The solvents and basic compounds used are as follows. It is noted thatthe solvents contained 0.05% by weight of surfactant Florade FC-430(Sumitomo 3M).

PGMEA: propylene glycol methyl ether acetate

CyHO: cyclohexanone

TBA: tributylamine

TEA: triethanolamine

TMMEA: trismethoxymethoxyethylamine

TMEMEA: trismethoxyethoxymethoxyethylamine

These resist solutions were spin-coated onto silicon wafers, then bakedon a hot plate at 130° C. for 90 seconds to give resist films having athickness of 0.5 μm. The resist films were exposed using an KrF excimerlaser stepper (Nikon Corporation; NA 0.5), then baked (PEB) at 130° C.for 90 seconds, and developed with a solution of 2.38% TMAH in water,thereby giving positive patterns.

The resulting resist patterns were evaluated as described below. First,the sensitivity (Eth, mJ/cm²) was determined. Next, the optimal dose(Eop, mJ/cm²) was defined as the dose which provides a 1:1 resolution atthe top and bottom of a 0.30 μm line-and-space pattern, and theresolution of the resist under evaluation was defined as the minimumline width (μm) of the lines and spaces that separated at this dose. Theshape of the resolved resist pattern was examined under a scanningelectron microscope.

The composition and test results of the resist materials are shown inTable 1.

Comparative Example

For comparison purposes, resist compositions were formulated andexamined for resolution upon KrF excimer laser exposure.

Comparative Examples 1 to 4

Resist compositions were prepared as in Example I except that Polymers 7and 8 were used as the base resin, in accordance with the formulationshown in Table 2.

There resist materials were similarly evaluated. The composition andtest results of these resist materials are shown in Table 2.

TABLE 1 Base Photoacid Dissolution Basic Optimum resin generatorregulator compound Solvent dose Resolution Example (pbw) (pbw) (pbw)(pbw) (pbw) (mJ/cm²) (μm) Shape I-1  Polymer 1 PAG 1(1) TBA PGMEA 22.00.24 rectangular (80) (0.125) (560) I-2  Polymer 2 PAG 1(1) TBA PGMEA21.0 0.24 rectangular (80) (0.125) (560) I-3  Polymer 3 PAG 1(1) TBAPGMEA 20.5 0.24 rectangular (80) (0.125) (560) I-4  Polymer 4 PAG 1(1)TBA PGMEA 19.5 0.24 rectangular (80) (0.125) (560) I-5  Polymer 5 PAG1(1) TBA PGMEA 18.0 0.24 rectangular (80) (0.125) (560) I-6  Polymer 6PAG 1(1) TBA PGMEA 20.5 0.24 rectangular (80) (0.125) (560) I-7 Polymer2 PAG 2(1) TBA CyHO 21.5 0.24 rectangular (80) (0.125) (560) I-8 Polymer 2 PAG 2(1) TEA CyHO 24.5 0.22 rectangular (80) (0.125) (560)I-9  Polymer 2 PAG 2(1) TMMEA CyHO 22.0 0.22 rectangular (80) (0.125)(560) I-10 Polymer 2 PAG 2(1) TMEMEA CyHO 21.5 0.22 rectangular (80)(0.125) (560) I-11 Polymer 6 PAG 1(1) DRR 1 TEA PGMEA 22.0 0.24rectangular (70) (10) (0.125) (560) I-12 Polymer 6 PAG 1(1) DRR 2 TEAPGMEA 23.5 0.24 rectangular (70) (10) (0.125) (560) I-13 Polymer 6 PAG1(1) DRR 3 TEA PGMEA 25.0 0.24 rectangular (70) (10) (0.125) (560) I-14Polymer 6 PAG 1(1) DRR 4 TEA PGMEA 24.0 0.22 rectangular (70) (10)(0.125) (560) I-15 Polymer 6 PAG 1(1) ACC 1 TEA PGMEA 24.0 0.24rectangular (70) (4) (0.125) (560) I-16 Polymer 6 PAG 1(1) ACC 2 TEAPGMEA 22.0 0.24 rectangular (70) (4) (0.125) (560)

TABLE 2 Compar- Base Photoacid Dissolution Basic Optimum ative resingenerator regulator compound Solvent dose Resolution Example (pbw) (pbw)(pbw) (pbw) (pbw) (mJ/cm²) (μm) Shape 1 Polymer 7 PAG 1(1) TBA PGMEA — —not (80) (0.125) (560) resolved 2 Polymer 8 PAG 1(1) TBA PGMEA — — not(80) (0.125) (560) resolved 3 Polymer 7 PAG 1(1) DRR 4 TEA PGMEA 30.00.28 T-top (80) (10) (0.125) (560) 4 Polymer 8 PAG 1(1) DRR 4 TEA PGMEA28.5 0.28 T-top (80) (10) (0.125) (560)

It is seen from Tables 1 and 2 that the resist compositions within thescope of the invention have a very high sensitivity and resolution uponKrF excimer laser exposure, as compared with prior art compositions.

Example II

Resist compositions were formulated using inventive polymers andexamined for resolution upon ArF excimer laser exposure.

Examples II-1 & II-2

Evaluation of Resist Resolution

Resist compositions were prepared as in Example I in accordance with theformulation shown in Table 3.

The resulting resist solutions were spin-coated onto silicon wafers,then baked on a hot plate at 130° C. for 90 seconds to give resist filmshaving a thickness of 0.5 μm. The resist films were exposed using an ArFexcimer laser stepper (Nikon Corporation; NA 0.55), then baked (PEB) at130° C. for 90 seconds, and developed with a solution of 2.38% TMAH inwater, thereby giving positive patterns.

The resulting resist patterns were evaluated as described below. First,the sensitivity (Eth, mJ/cm²) was determined. Next, the optimal dose(Eop, mJ/cm²) was defined as the dose which provides a 1:1 resolution atthe top and bottom of a 0.25 μm line-and-space pattern, and theresolution of the resist under evaluation was defined as the minimumline width (μm) of the lines and spaces that separated at this dose. Theshape of the resolved resist pattern was examined under a scanningelectron microscope.

The composition and test results of the resist materials are shown inTable 3.

TABLE 3 Base Photoacid Dissolution Basic Optimum resin generatorregulator compound Solvent dose Resolution Example (pbw) (pbw) (pbw)(pbw) (pbw) (mJ/cm²) (μm) Shape II-1 Polymer 2 PAG1 (1) — TBA PGMEA 20.50.18 rectangular (70) (0.125) (560) II-2 Polymer 6 PAG1 (1) DRR4 (10)TEA PGMEA 19.5 0.18 rectangular (70) (0.125) (560)

It is seen from Table 3 that the resist compositions within the scope ofthe invention have a very high sensitivity and resolution upon ArFexcimer laser exposure.

Japanese Patent Application Nos. 2000-060637 and 2000-076537 areincorporated herein by reference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

What is claimed is:
 1. A polymer comprising recurring units of thefollowing general formula (1) and having a weight average molecularweight of 1,000 to 500,000,

wherein R¹ is hydrogen, methyl or CH₂CO₂R³, R² is hydrogen, methyl orCO₂R³, R³ is a straight, branched or cyclic alkyl group of 1 to 15carbon atoms, R⁴ is hydrogen, a straight, branched or cyclic alkyl groupof 1 to 15 carbon atoms, a straight, branched or cyclic alkoxyalkylgroup of 2 to 15 carbon atoms, or a straight, branched or cyclic acylgroup of 1 to 15 carbon atoms, R⁵ and R¹⁵ each are an acid labile group,at least one of R⁶ to R⁹ is a carboxyl or hydroxyl-containing monovalenthydrocarbon group of 1 to 15 carbon atoms, and the remainders areindependently hydrogen or a straight, branched or cyclic alkyl group of1 to 15 carbon atoms, or R⁶ to R⁹, taken together, may form a ring, andwhen they form a ring, at least one of R⁶ to R⁹ is a carboxyl orhydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms,and the remainders are independently a single bond or a straight,branched or cyclic alkylene group of 1 to 15 carbon atoms, at least oneof R¹⁰ to R¹³ is a monovalent hydrocarbon group of 2 to 15 carbon atomscontaining a —CO₂— partial structure, and the remainders areindependently hydrogen or a straight, branched or cyclic alkyl group of1 to 15 carbon atoms, or R¹⁰ to R¹³ , taken together, may form a ring,and when they form a ring, at least one of R¹⁰ to R¹³ is a divalenthydrocarbon group of 1 to 15 carbon atoms containing a —CO₂— partialstructure, and the remainders are independently a single bond or astraight, branched or cyclic alkylene group of 1 to 15 carbon atoms, R¹⁴is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkylgroup containing such a polycyclic hydrocarbon group, Z is a trivalenthydrocarbon group of 1 to 10 carbon atoms, or Z forms a ring with R¹,and in this event, R¹ is methylene and Z is a tetravalent hydrocarbongroup of 1 to 10 carbon atoms, X is —CH₂— or —O—, k is equal to 0 or 1,x is a number of more than 0, a, b, c and d are 0 or positive numbers,satisfying x+a+b+c+d=1.
 2. The polymer of claim 1 wherein the acidlabile groups represented by R⁵ and R¹⁵ in formula (1) are selected fromthe class consisting of groups of the following general formulae (L1) to(L4), tertiary alkyl groups of 4 to 20 carbon atoms, trialkylsilylgroups in which each alkyl moiety has 1 to 6 carbon atoms, oxoalkylgroups of 4 to 20 carbon atoms, and mixtures of any of the foregoing,

wherein R^(L01) and R^(L02) each are hydrogen or a straight, branched orcyclic alkyl group of 1 to 18 carbon atoms, R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms which may contain a heteroatom such as oxygen atom, a pair of R^(L01) and R^(L02), R^(L01) andR^(L03), or R^(L02) and R^(L03) may form a ring, each of R^(L01),R^(L02) and R^(L03) is a straight or branched alkylene group of 1 to 18carbon atoms when they form a ring, R^(L04) is a tertiary alkyl group of4 to 20 carbon atoms, a trialkylsilyl group in which each alkyl moietyhas 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or agroup of formula (L1), R^(L05) is a straight, branched or cyclic alkylgroup of 1 to 8 carbon atoms or a substituted or unsubstituted arylgroup of 6 to 20 carbon atoms, R^(L06) is a straight, branched or cyclicalkyl group of 1 to 8 carbon atoms or a substituted or unsubstitutedaryl group of 6 to 20 carbon atoms, R^(L07) to R^(L16) are independentlyhydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms whichmay contain a hetero atom, R^(L07) to R^(L16), taken together, may forma ring, and each of R^(L07) to R^(L16) represents a divalent hydrocarbongroup of 1 to 15 carbon atoms which may contain a hetero atom, when theyform a ring, or two of R^(L07) to R^(L16) which are attached toadjoining carbon atoms may bond together directly to form a double bond,y is an integer of 0 to 6, m is equal to 0 or 1, and n is equal to 0, 1,2 or 3, satisfying 2m+n=2 or
 3. 3. A resist composition comprising thepolymer of claim
 1. 4. A process for forming a resist pattern comprisingthe steps of: applying the resist composition of claim 3 onto asubstrate to form a coating, heat treating the coating and then exposingit to high-energy radiation or electron beams through a photo mask, andoptionally heat treating the exposed coating and developing it with adeveloper.